1. Field of Invention
The present invention relates to a polarization-converting unit for converting luminous flux emitted from a light source into one kind of polarized light, and a projector for forming a projected image by modulating, magnifying and projecting the polarized light.
2. Description of Related Art
Recently, the number of environments in which projectors are used has increased, and apart from being used solely for presentations in office meetings or meetings on business trips, projectors are now being used at technical meetings in research and development divisions, etc., for capturing CAD/CAM/CAE data therein in order to magnify and project them, or at various seminars and learning courses. Projectors are also being used in school classes where audiovisual education is performed. Projectors are also used for studying therapeutic methods and for performing medical guidance by projecting medical images and data such as CT scans and MRI. Projectors are also being used for efficiently addressing people gathered at exhibitions or conventions.
Presently, because projectors are being used in various environments, the projectors are subject to various requirements relating to their specifications and functions, such as light-weight compact models pursuing portability, high-luminance and high-resolution models pursuing image quality, and value-added models capable of connecting to various digital equipment and mobile tools.
Since further increases in the number of environments in which the projectors will be used is anticipated, more advanced value-added projectors are being vigorously developed in light of the new environments in which projectors will be used.
One type of optical element used for the projector is a polarization-converting element for converting luminous flux emitted from a light source into one kind of polarized light. Such a polarization-converting element is arranged close to the light-incident side of a lens array or the light-emerging side of the lens array, depending on the structure of an optical system. In either of these cases, the position thereof is properly adjusted relative to the lens array.
A luminous-flux dividing element is typically positioned on the front face of the light source (light-emerging side). Therefore, in the positional relationship between the polarization-converting element and the lens array, when the polarization-converting element is arranged in the light-incident side of the lens array, it is also necessary to adjust the positional relationship between the polarization-converting element and the luminous-flux dividing element which is further located in the light-incident side. In contrast, when the polarization-converting element is arranged in the light-emerging side of the lens array, the positional adjustment should be performed between the lens array and the luminous-flux dividing element.
However, since the positional adjustment between the polarization-converting element, the lens array, and the luminous-flux dividing element is individually performed on a supporting body that supports these elements, the adjustment operation takes time. Therefore, it has been attempted to integrally form and unitize the polarization-converting element and the lens array, and to simultaneously positionally adjust both of these elements with the unitization. In such a case, on the supporting body, only the positional adjustment between this unit and the luminous-flux dividing element may be performed, thereby simplifying the adjustment operation.
On the other hand, since the polarization-converting element and the lens array are liable to reach a high temperature by incidence and emergence of light, they need to be cooled by cooling air.
The polarization-converting element and the lens array must be cooled, however, it is difficult to efficiently cool the polarization-converting element and the lens array, both of which are unitized together.
It is therefore an object of the present invention to provide a polarization-converting unit capable of being sufficiently cooled, even when polarization-converting elements and a lens array are unitized together, and to provide a projector using the polarization-converting unit.
A polarization-converting unit according to the present invention includes: polarization-converting elements, a lens array arranged so as to oppose the polarization-converting elements and to define a clearance therebetween, and a holding frame that integrally holds the polarization-converting elements and the lens array together, the holding frame being provided with at least a pair of openings to allow cooling air to flow-in and flow-out of the clearance.
In such a structure, the holding frame is provided in order to unify the polarization-converting elements and the lens array together; the holding frame is provided with the openings to allow cooling air to flow-in and flow-out therethrough, so that cooling air can flow through the clearance between the polarization-converting elements and the lens array, thereby the polarization-converting elements and the lens array are sufficiently cooled from faces opposing each other, which achieves the object of the present invention.
In a polarization-converting unit according to the present invention, one of the openings of the holding frame may be preferably provided with a current guide that guides cooling air toward the clearance.
In such a structure, the current guide is provided in the flow-inlet-side opening for cooling air, so that a larger amount of cooling air can securely flow into the clearance within the polarization-converting unit, thereby enhancing the cooling efficiency of the polarization-converting elements and the lens array.
In a polarization-converting unit according to the present invention, the current guide may be preferably formed to have a smooth curved surface.
In such a structure, the flow of cooling air becomes smooth in the current guide, so that flow-in and flow-out of the cooling air are efficiently performed, thereby furthermore enhancing the cooling efficiency. Also, impulsive noises are difficult to be produced when cooling air collides against the current guide so as to reduce noises.
A projector according to the present invention includes: a light source and a polarization-converting unit as disclosed above, wherein luminous flux emitted from the light source is magnified and projected so as to form a projected image after being modulated.
In such a structure, a projector capable of excellently cooling polarization-converting elements and a lens array can be provided by using the polarization-converting unit described above.
A projector according to the present invention may preferably further include a sirocco fan that exhausts cooling air to cool the air-flow-inlet-side opening disposed in the holding frame of the polarization-converting unit.
In such a structure, as cooling air is fed by the sirocco fan, reduction in noises is promoted compared to when an axial-flow fan is used, for example.
A projector according to the present invention may preferably further include a duct disposed between the sirocco fan and the cooling-air-flow-inlet-side opening.
In such a structure, by arranging the duct, all the cooling air exhausted from the sirocco fan can be fed to the opening of the polarization-converting unit, thereby also enhancing the cooling efficiency.
In a projector according to the present invention, a portion of the duct may be preferably formed of an outer case.
In a projector according to the present invention, a portion of the duct may be preferably formed of a supporting body that holds the polarization-converting unit.
In these structures, the duct does not need to be separate and distinct from the outer case and the supporting body, thereby enabling the number of parts and the cost to be reduced.
In a projector according to the present invention, the sirocco fan may be preferably arranged in the supporting body.
In such a structure, because the sirocco fan and the supporting body can be unified together in advance before assembling them in the outer case, etc., the assembling operation is easier than that in which these parts are individually assembled in the outer case, which enhances the efficiency during the assembling.
In a projector according to the present invention, the duct may preferably communicate with the front face (light-emerging side) of the light-source.
In such a structure, cooling air can also be fed toward the optical elements, such as the luminous-flux dividing element arranged between the light source and the polarization-converting unit, so that most of the optical elements arranged close to the light source can be cooled.
A projector according to the present invention may further include: a filter that shields ultraviolet radiation (UV filter), and a luminous-flux dividing element, both of which are arranged on the front face of the light source. In such a structure, the UV filter and the luminous flux dividing element, both of which are optical elements placed close to the light source, are sufficiently cooled.
In a projector according to the present invention, the bottom surface of an outer case may be preferably provided with a concave portion at a position corresponding to that of the sirocco fan.
In such a structure, the sirocco fan is arranged so as to sink into the concave portion on the bottom face, so that the top face level of the sirocco fan can be lowered, enabling the thickness of the entire projector to be reduced.
In a projector according to the present invention, the sirocco fan may be preferably arranged in the light-emerging side of the polarization-converting unit.
In such a structure, the sirocco fan is arranged in the side opposite to the light source relative to the polarization-converting device, so as to increase flexibility for positioning the sirocco fan and eliminate the parts around the light source, thereby securely providing the opening for replacing a lamp, etc.